Image Forming Apparatus With Test-Chart Magnification Correction
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Solution Overview
Problem
Existing image forming apparatuses struggle to accurately correct partial magnification changes in the sub-scanning direction due to variations in sheet thickness, surface characteristics, and toner density, which cause inconsistencies in sheet conveying velocity.
Innovation Solution
The apparatus forms a test chart with varying toner densities and reads it to calculate the partial and total magnification deviations, adjusting the rotation velocity of the secondary-transfer outer roller based on these measurements to maintain accurate image size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the secondary-transfer outer roller velocity is controlled based on average sheet velocity measurement, then total magnification change is corrected, but partial magnification change in different toner bearing areas cannot be corrected
Solution Approach 1:
The patent divides the sheet into multiple measurement regions based on toner bearing areas. Instead of measuring average velocity across the entire sheet, the system segments the measurement into first and second measurement regions with different toner densities, allowing independent velocity measurement and correction for each region.
Solution Approach 2:
The patent applies local quality by measuring and correcting sheet velocity independently for different regions with different toner bearing characteristics. The control unit calculates first and second sheet velocities separately for first and second measurement regions, and adjusts the secondary-transfer outer roller velocity specifically for areas with significant partial magnification changes.
2Adaptability or versatility
If sheets with different thicknesses and surface characteristics are fed, then printing versatility is improved, but sheet conveying velocity varies causing magnification changes
Solution Approach 1:
The patent implements feedback control by measuring the actual sheet velocity in different regions using the reading unit, comparing it with the intended velocity, and adjusting the secondary-transfer outer roller velocity accordingly. The control unit continuously monitors sheet velocity through test chart measurements and corrects velocity deviations to maintain consistent image size across different sheet types.
Solution Approach 2:
The patent applies dynamics by making the secondary-transfer outer roller velocity adjustable and adaptive rather than fixed. The system dynamically changes the roller velocity based on real-time measurements of sheet velocity and characteristics, allowing the printing system to adapt to different sheet thicknesses, surface characteristics, and toner densities while maintaining precise image dimensions.
Data Source
AI summary
The image forming apparatus forms a test chart on an image bearing member, the test chart including a plurality of test images including a first test image of a first density and a second test image formed at a position different from a position of the first test image in a conveying direction of a recording medium, the second test image having a second density different from the first density. The image forming apparatus transfers the test chart to the recording medium with a transfer roller and controls the rotation velocity of the transfer roller when the recording medium passes through a transfer portion based on a result of reading the test chart on the recording medium with a reading unit.